This study will create Alzheimer 's disease risk profiles for defined combinations of genotypes and environmental exposures. This study will carry out a molecular epidemiologic study to identify genetic and environmental risks factors using state of the art techniques. The following will be done during the course of this study 1) Recruit both Alzheimer's patients and cognitively normal aged veterans. 2) Evaluate gene interaction in Alzheimer's disease. 3) Evaluate gene-environment interactions on the risk of Alzheimer's disease. These procedures should initially address the question as to whether certain genes either independently or synergistically modify the risk of Alzheimer's disease. This study will also determine whether certain environmental factors (smoking, alcohol consumption etc.) can modify the risk of AD and whether this effect is dependent on certain genetic backgrounds. This study will provide information that will be useful in designing therapies, develop risk factor profiles to be further tested in future studies, designating patients for specific therapies based on genetic factors and providing data and genetic material for future studies. This study will also provide a cohort of older and well characterized cognitively normal veterans for prospective genetic epidemiological studies on aging.